Along with the rapid development of electronic industry, it is not uncommon to play films with advance sound and visual effects on computers anymore. Therefore, the requirement for video and audio performance has become more and more stringent. Except for the need of higher resolution and visual quality, in the field of audio frequency and sound effect, stereo sound effect has gradually replaced mono sound effect. However, the traditional stereo sound effect generates sound through lateral panning of sounds between two speakers to simulate the real three-dimensional sound source movements, and does not actually generate sounds in a three-dimensional space. Another type of surrounding sound generates three-dimensional sounds through multiple speakers, yet it is impossible to precisely locate sounds in a space. Therefore, the sound effect is unsatisfactory.
In recent years, head-related transfer function (HRTF) has been widely used in the field of three-dimensional sound locating technique. Because HRTF simulates the sound effect model heard by a human ear in a three-dimensional space and the parameters corresponding to the three-dimensional sound effect at every spot of the space are determined by its distance, azimuth, and elevation, the listener feel like within the real atmosphere of the sound while playing a film. However, the method of utilizing two sets of speakers to simulate three-dimensional sound effect still exhibits some shortcomings and limitations. For example, those speakers need better frequency response, the positions of the speakers need to be leveled with human ear, the locations of the listener and the speakers should be arranged so as to become an equilateral triangle, the rear surrounding effect should be realistic enough, and the sweet spot which is the area actually generating surrounding sound effect needs to be large enough, otherwise not all people within the space are able to enjoy the sound effect. Therefore, the structure of utilizing four or more speakers is then introduced.
Please refer to FIG. 1A of the prior art, the 5.1D sound system 10A, widely used among family theaters, includes four satellite speakers, each at the front left, front right, rear left, and rear right directions of the listener 144 120, i.e., front left (FL) speaker 110, front right (FR) 112, rear left (RL) 114, rear right (RR) 116, respectively, and with an additional sub woofer 118 to become a five-speaker system. Finally, the popular 5.1D sound system 10A also includes a voice speaker 106 near the screen 104 to play front scene voices, such as the dialogues between actors.
Generally speaking, the family theater system stated above can be controlled by a computer system 102, such as a personal computer (PC), through a sound control unit 1022 (e.g., a sound card) connected with three pairs of transmission lines 122, 124, and 126 to transmit the sound effect data needed by the six stated speakers to a control circuit 108A. Later on, the sound effect data is transferred to FL speaker 110, FR speaker 112, RL speaker 114, RR speaker 116, voice speaker 106, and sub woofer 118 separately through transmission lines 128, 130,132,134, 136, and 138 to generate sound. When the listener 120 watches film, listens to music, or plays computer game, the required three-dimensional sound effect can be realistically generated by the stated sound system 10A. Among the stated speakers, except the sub woofer 118 is used to generate low frequency sound, all the other speakers, including FL speaker 110, FR speaker 112, RL speaker 114, and RR speaker 116, are used to play mid and high frequency sound.
Besides, the conventional sound system 10A can only single-directionally receive and process the sound effect data from the computer system 102, but it can't transmit its status data back to the computer system 102, which is inconvenience while using. For example, human ear can't distinguish the directionality of low frequency sound and is insensitive to low frequency (e.g., 170 Hz) sound. In other words, the wattage of the sub woofer 118 has to increase a great deal for the human ear to sense the difference. On the contrary, human ear is quite sensitive to mid and high (e.g., 1–20 KHz) frequency sounds, therefore the wattage of general sub woofer 118 is much greater than other types of speakers, like the two stated speakers constructed in 40 and 5 watts. On the other hand, most conventional speakers need to be continuously kept at stand-by state and wait for the transmission of sound effect data in order to generate sounds. Therefore, about half (i.e., 50%) of the electrical power provided to the speakers is used to maintain the stand-by state and becomes dissipation heat in order to keep the speakers from burning up caused by overheating. Furthermore, while utilizing the stated speakers, if the listener 120 wants to adjust sound volume or sound quality or even switch the speakers on or off, the computer system 102 is lacking the related assisting user interface or accessories, so as that the listener 120 has to be in front of a speaker and lowers his or her body (or even lie on the floor) to adjust the speaker through control buttons. Some high-end sound and audio systems are equipped with additional extension wires to simplify the adjusting procedure. However, when the listener 120 needs to adjust the sound effect of entire sound field, all speakers need to be undergoing constant adjustment, which is a very inconvenient process. There is a great need for easier sound control system and method in order to overcome the difficulties faced by the prior art.